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Skanska’s green construction college gets a little help from BIM

Councillors are hoping Essex’s new college campus will help kick-start the regeneration of a town centre.

Project: South Essex College, New Thurrock Campus
Client: South Essex College
Contract value: £34m
Region: South-east
Main contractor: Skanska
Project manager: Turner and Townsend
Architect: KSS Group
Structural engineer: Skanska Technology
Engineer: Arup
Piling subcontractor: Cementation Skanska
M&E subcontractor: Skanska Rashleigh Weatherfoil
Start date: January 2013
Completion date: June 2014

Walk down the High Street towards the widening estuary of the River Thames at Grays and it is easy to see why local authority Thurrock Council wants to use this part of the Essex town to kick-start its regeneration.

With views straight down the pedestrianised street, across the Grays Town Wharf to the river and Kent beyond, the area has more than enough potential to anchor the rest of the town centre.

Part of the regeneration focuses on the construction of a new college campus for South Essex College.

It will offer courses in construction, engineering and new technology, as well art, hair and beauty and will draw students into Grays from around the wider Essex area.

Main contractor Skanska has the job of providing client South Essex College with its new campus on a site sourced from the local authority.

“It used to be the car park for the Thurrock Council offices and they worked out an arrangement with the college,” says Skanska UK Construction project director Steve Arthrell.

Getting the finance in place

The scheme will see £45m pumped into the overall development, with Skanska delivering the campus under a £34m design-and-build contract with the client.

“It was initially won under an open tender in 2010 but working out the financial and funding side held things up,” Mr Arthrell explains.

“Once all the funding was lined up we were formally awarded the contract with a start date of January 2013. It is a 78-week programme and we are due to hand over the scheme in July 2014.”

The team had carried out enabling works on the site before the January start date, with small-scale building demolition work and utility diversions around the site.

The main stormwater and foulwater sewer that dissects the site has not been diverted, however, and with the team prohibited from building over the top of the sewer the final design is actually split into two separate structures.

The west building features a lower ground floor, ground, first, second and third floor and will host the college restaurant, administrative offices, multi-use space, teaching areas and hair and beauty studios.

“It hasn’t been a full BIM integration across the scheme, but we have had a BIM co-ordinator in place. We have been using the ‘BIM 360’ software on tablet computers for everything relating to site and trade contractors”

Steve Arthrell, Skanska UK Construction

The east building features a ground, first and second floor only and will host the engineering and construction-based courses.

Both are built around a steel frame, which springs from the pile caps across a nominal 7.5 m grid with larger spans in the multi-use area.

The steel frame, installed by specialist contractor William Haley Engineering, is perfect for delivering these spans, with the advantage of being a lighter weight than the other options considered.

Floor slab design change

These included precast and prestressed concrete. The team also eventually changed the design of the floor slab with a shift from the precast concrete initially designed to a corrugated steel and cast in-situ concrete composite floor.

“There were one or two areas where installing precast planks would have been difficult,” Mr Arthrell says. “Changing to a composite slab made installation much easier.”

The client had also decided that it wanted a mechanically air conditioned building rather than a naturally vented facility.

This meant installing suspended ceilings to encase the mechanical and electrical services, which have been prefabricated by specialist producer Skanska Fabrications at its facility in Slough.

BIM lends a digital hand

The use of the composite floor meant a more slender slab and more room to install the services, but nevertheless it was a move that Mr Arthrell is convinced could have proven problematic if it hadn’t been for the use of building information modelling across the project.

“It hasn’t been a full BIM integration across the scheme, but we have had a BIM co-ordinator in place,” he says. “We have been using the ‘BIM 360’ software on tablet computers for everything relating to site and trade contractors.

“We don’t want to be coming back to fix leaks so waterproof concrete, although more expensive, was the best option”

Steve Arthrell, Skanska UK Construction

“The change from the precast to the composite and the services co-ordination was helped through by BIM. I don’t think it would’ve worked quite as well without it.”

Construction of the two buildings reflect their final use, with the east building featuring a robust externally clad brickwork and blockwork envelope.

The west building features externally clad lightweight insulated steel and plasterboard construction walls.

“Both buildings have facing brickwork until first-floor level apart from the curtain walling on the front and rear faces of the west building. Above that is the rainscreen cladding,” Mr Arthrell says.

Term timing challenge

The west building is critical to the construction of the college. It is lagging behind the east building thanks to the extra time spent bringing up the 300 mm-thick reinforced concrete walls that spring from the pile caps (see box), but the team is confident this will not affect the project’s completion, which is set for July 2014.

“It needs to be ready for the college to be able to open in time for the September 2014 term. We’re happy at where we are on the programme,” Mr Arthrell says.

Already the building is drawing attention to this part of the town centre. When it finally opens its doors to the first wave of students, the local authority is hopeful it will prove just as beneficial in drawing in further investment and regeneration to an area that is ripe to be thrown a rejuvenative lifeline.

Asbestos and chalk pose foundations questions

Across the Grays site the team has installed a forest of piles to help support the final structure of the east and west buildings at the South Essex College.

Specialist foundations contractor Cementation Skanska installed 500 piles around the site, each of them 450 mm-diameter CFA running through the underlying chalk beds at around 10 m and on to full depth at between 18 and 20 m.

The team was concerned that because of the chalk beds there may be soft spots where the calcium carbonate of the chalk had been dissolved thanks to water percolating through the rock.

These can cause subsidence across subsurface layers and affect the buildings above.

“There was some unease that there may be areas of chalk solution across the site, but we didn’t hit anything,” Mr Arthrell says.

In fact, the only issue with the ground occurred when the team found an area of buried asbestos beneath the car park surface.

Although an isolated pocket, it was still enough to hold up work on the scheme while the required paperwork and notification work was completed.

There are three or four piles to each pile cap across the site, except for the west building where there is a reinforced concrete lower ground floor basement.

This forms the main plant room areas as well as the double-height performance space and was built using waterproof concrete to an environmental grade 3 basement under BS8102.

“The water table is around 8 m below the surface,” Mr Arthrell says. “We used waterproof concrete really because of the surety it offers.

“We don’t want to be coming back to fix leaks so waterproof concrete, although more expensive, was the best option.”

 

Champagne-style toilet system helps hit green goals

Like most construction projects, methods to alleviate environmental impact are important to the success of the campus. The delivery team is targeted with providing a building with a BREEAM Very Good rating.

With an array of photovoltaic cells on the roof that will help offset some of the power demand for the building and various steps taken throughout the construction process to use recycled, reclaimed and green products, the scheme is well on its way to meeting those commitments.

But it is the innovative rainwater harvesting system that will store water for use throughout the building’s system of toilets that is different to standard systems.

Here, a holding tank Pipex system designed by Arup allows water to percolate through the toilet cisterns across the building in a similar way to filling a pyramid of champagne glasses.

“There is an override freshwater pump if required but the system uses the roof as a holding vessel,” Mr Arthrell says. “It does take up a little more room in the toilets but there is no real difference in installation.”

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